The proposed research examines the differences, in terms of processes and impacts on functioning and mental health, between adolescents' relationships with volunteer mentors, who become involved with youth through their participation in mentoring programs, and with natural mentors, who are nonparental adults such as extended family members or neighbors from the youth's own communities. A deeper understanding of the ways in which different types of supportive relationships function can inform the design of programs and policies seeking to improve youth outcomes. Data from Public/Private Ventures' rigorous evaluation of the Big Brothers Big Sisters mentoring program is used in this investigation. Although prior studies have identified significant benefits among youth with volunteer mentors, the proposed research will compare these benefits with those associated with natural mentors, testing for mediating influences of the gender, age, income level of adolescents as well as mentoring adults. Despite growing interest in the benefits of mentoring for at-risk youth, this study will be the first to compare these two types of mentoring relationships.